Transformer



F. REISINGER July 10, 1962 TRANSFORMER Filed June 30. 1959 INVENTOR:Franz Reisin er atent fiice 3,043,900 Patented July 10, 1962 3,043,900TRANSFORMER Franz Reisinger, 21/6 Piigerimgasse, Vienna 15, AustriaFiled June 30, 1959, Ser. No. 824,011 Claims priority, applicationAustria July 15, 1958 p 2 Claims. (Cl. 17412) In transformers it is wellknown to use an expansion tank arranged at the height of the bushings,which serves to compensate for the differences of the oil volumesaccording to the different operating temperatures during action.

Air-drying apparatus well known in transformers for great capacity arenot suitable for distributing transformers, necessitating permanentservice and surveillance. Therefore in distributing transformers the oillevel of the expansion tank has an immediate contact with the outsideair and the oil having a rather high temperature in the expansion tankabsorbs greedily the humidity of the outer air deteriorating itselectrical-insulation value. The atmospheric oxygen absorbed by thetransformer oil adds to the aging of the oil. Frequent oil-changing isnecessary for these transformers to prevent heavy damage resulting fromdeteriorated oil. According to the finctuation of the oil volume andthus of the oil level, the

inner walls of the expansion tankbecome attacked alternately by thetransformer oil and by the atmospheric 7 oxygen, causing condensationresulting in heavy corrosion. In these distributing transformersparticles of the corrosive incrustations loosened from the walls arriveinto the oil tank and to the windings often causing heavy damage. Theloosening of the particles is advanced by the frequent change inlocation as it is usual with distributing transformers.

' It is also known to avoid the disadvantage resulting from breathing ofthe transformer, apart from the use of the above mentioned drying means,as for instance silicagel, by providing a cushion of nitrogen above theoil level or to seal off the oil volume by a rubber membrane, saidmembrane curving down or up from a mid-position, according to the oiltemperature and thus of the oil level. The attachment of the membrane issubject to a special (two-part) structure of the expansion tank. Theinventive arrangement avoids the above described disadvantages whichinvolve expensive air-drying apparatus requiring permanent service andsurveillance and removing only the injuirous influence of theatmospheric moisture. The harmful influence of the atmospheric oxygen isnot taken into account by these air-drying apparatus. I

The invention also does not need a special structure of the expansiontank.

The chief object of the invention is to seal ofi in electricalapparatus, especially transformers and choke coils, the oil volumediffering according to the oil temperature. The oil volume is sealed offwith respect to the atmos phere by providing an oil-filled sack-likeexpansion body arranged in dead spaces of the transformer housing,especially near the bottom of the housing between the structural memberssupporting the active parts of the electrical transformer. The expansionbody is made of a well extensible and foldable, oil-resistant materialwhich is impermeable to gas and which is connected by means of a hoseline to an open expansion tank of the well known type arranged above thehousing. The housing has a filling pipe reaching up to the height of theupper edge of the expansion tank. The advantages of the inventivearrangement will become apparent from the following description and theaccompanying drawing. The novel features which characterize theinvention will be pointed out in the claims annexed to thisspecification.

In the drawing, FIG. 1 shows one embodiment of the electricaltransformer system in elevation and partly in section, and FIG. 2 is asimilar view of a modified arrangement according to the invention.

In FIG. 1, the expansion tank 2 is arranged above the transformerhousing 1. Within the housing there are the windings and core 3 arrangedin a manner which is not described in detail. In the illustratedembodiment, the expansion body 4 is arranged between the housing bottomand the lower core yoke. The body 4 therefore occupies a space generallynot important for the cooling or the insulating of the transformer. Thehose line 5 joins the body 4 to the lead-in 6 and the usual pipe line 7is connected to the expansion tank 2. Moreover the filling pipe 8serving to fill with oil the whole transformer housing is arranged onthe cover of the housing. Pipe 8 is hermetically closed by a cap 10. Onthe pipe, there can be provided a high-pressure relief valve or abreaking diaphragm in a Well known manner, not illustrated in thedrawing. The volume of the expansion body 4 is equal to or greater thanthe maximum difference of oil volume of the acting oil.

In the following, the oil filling process will be described. By means ofpipe 8 the transformer housing becomes filled with oil while theexpansion tank is empty. When the housing is completely filled theexpansion body 4 is entirely pressed down and its air-volume has escapedby way or the hose line 5, the pipe 7 and the expansion tank 2. Then,the opening of pipe 8 is closed by the cap 10 and the expansion tank 2is being completely filled with oil. When later some oil is beingdrained by the oil-drain valve 9 at the bottom of the housing, exactlythe same oil volume will escape from the expansion tank 2 into theexpansion body 4 thereby preserving in every case the complete fillingof the transformer housing 1. At the oil gauge (not illustrated) thereare arranged several marks according to the oil levels at various oiltemperatures. Knowing the filling temperature of the oil there isdefined thereby the amount of oil volume to escape from the expansiontank 2 so as to fill (by opening the oil-drain valve 9 of thetransformer housing) the expansion body 4 with exactly the oil volumewhich is necessary to reach the oil level, that is the special mark,corresponding with the filling temperature and which has to be pressedback to the expansion tank 2 when the oil has reached its highesttemperature.

' In a favorable embodiment of the device according to the invention,means are provided for connecting the bag 4 with the active transformerpart 3, so that these parts form a unit with the bag, which as a wholecan be taken out of the housing 1 when inspection or repair becomesnecessary.

This embodiment of the invention is shown in FIG. 2 wherein similarelements are designated by like numerals. In this embodiment asupporting structure 13, e.g. a plate made of fiber board, is providedfor the transformer core 3 which is mounted on wooden blocks 11. The bag4 is carried by a number of U-shaped bands 12 anchored in the plate 13.This arrangement makes it possible to remove the core and bag as a unit.

The advantages of the inventive arrangement are described in thefollowing. The walls of the expansion body consist of a material havinga neoprene base. There is no danger for the oil in the transformerhousing to become soiled by the oxygen or the atmospheric humidity byway of diffusion through the walls of the expansion body. In the latterthe oil is enriched with these impurities as oxygen, atmospherichumidity, or solid particles, but this oil is not in contact with theactive oil in the transformer housing. A further advantage by using theinventive arrangement is obtained by eliminating the difficultiesarising by the corrosive action on the walls of the expansion tank. Theinner walls of the expansion tank have to be treated with a suitableprotective agent 3 against corrosion. It is not necessary to take careof the chemical influences of this protective agent on the oil in theexpansion tank, because the oil of the expansion tank never serves toinsulate but only for the filling of the expansion body. The insulatingquality of this oil is therefore not important.

The invention and its advantages will be understood from the foregoingdescription. It is apparent that various changes may be made in theform, construction and arrangement of the parts Without departing fromthe spirit and scope of the invention, the form hereinbefore describedand illustrated in the drawing being merely a preferred embodimentthereof and several other forms of application to electrical oil-filledtransformers are feasible.

What is claimed is:

1. An electrical transformer system having a housing with a cover and anoil-drain valve at the bottom; pipe means for filling the housing tocapacity With oil and including a high-pressure relief valve, saidsystem comprising a core and coil assembly submerged in the oil, saidoil being completely enclosed in said housing and sealed off from theouter air, an expansion tank arranged above the housing, said expansiontank being filled With oil and having communication With the surroundingatmosphere, a bag-like expansion body arranged in the interior of saidhousing at a dead space between structural members supporting the activetransformer parts and consisting of extensible, and pliable,oil-resistant and gasimpermeable material, the interior of said bagbeing completely shut oif from contact with the oil in said casing, andmeans being provided for connecting said baglike body with saidexpansion-tank for at least partly filling the bag with oil from theexpansion tank for equalizing the diiferences of oil volume at differentoperating temperatures, said connecting means including a hose line madeof similar material to that of the expansion body, a lead-in pipeconnected to said hose line, and pipe means for connecting said lead-inpipe to said expansion tank.

2. An electrical transformer system according to claim 1, wherein meansare provided for attaching said baglike expansion body to saidtransformer within the housing, so as to form a unit, said unit beingsuitable for lifting out of the housing as a Whole.

References Cited in the file of this patent UNITED STATES PATENTS1,227,404 Dubois May 22, 1917 1,933,313 Clark Oct. 31, 1933 2,826,629Reuschle Mar. 11, 1958 FOREIGN PATENTS 194,020 Switzerland Nov. 15, 1937578,471 Great Britain June 28, 1946 635,541 Great Britain Apr. 12, 1950705,145 Great Britain Mar. 10, 1954 914,269 Germany June 28, 1954

